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Power consumption and form drag of regular and fractal‐shaped turbines in a stirred tank
Author(s) -
Steiros K.,
Bruce P. J. K.,
Buxton O. R. H.,
Vassilicos J. C.
Publication year - 2017
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.15414
Subject(s) - drag , drag coefficient , mechanics , wake , fractal , wind tunnel , parasitic drag , radius , fractal dimension , impeller , zero lift drag coefficient , physics , geometry , materials science , mathematics , lift induced drag , mathematical analysis , computer security , computer science
Previous wind‐tunnel measurements have shown that fractal‐shaped plates have increased drag compared to square plates of the same area. In this study, the power consumption and drag of turbines with fractal and rectangular blades in a stirred tank are measured. Power number decreases from rectangular to fractal impellers by over 10%, increasingly so with fractal iteration number. Our results suggest that this decrease is not caused by the wake interaction of the blades, nor solely by the wake interaction with the walls either. Pressure measurements on the blades’ surface show that fractal blades have lower drag than the rectangular ones, opposite to the wind tunnel experiment results. All tested blades’ center of pressure radius increases with Re, while their drag coefficient decreases, a possible effect of the solid body rotation expansion with Re. Spectral analysis of the pressure signal reveals two peaks possibly connected to the blades’ roll vortices. © 2016 American Institute of Chemical Engineers AIChE J , 63: 843–854, 2017